1. Field of the Invention
The present invention is directed to the monitoring of physiological conditions of patients and, more particularly, to the leadless monitoring of such conditions.
2. Discussion of Related Art
In modern medicine, to properly diagnose and treat a patient, it is essential that health care providers have the ability to monitor various physiological conditions of the patient. Therefore, many electronic devices have been developed that monitor various physiological conditions. Examples of such devices include electrocardiograph (ECG) monitors, electroencephalographs (EEGs), blood oxygenation (SpO.sub.2) monitors, etc., as well as monitors that measure various combinations of the physiological conditions monitored by each of these devices.
Conventional patient monitoring devices generally employ one or more transducers to generate electronic signals indicative of physiological conditions of a patient, and use separate electronic units to receive these electronic signals and display such conditions to clinicians. These monitoring devices typically use cables to transmit the electronic signals from the transducer(s) to the display devices. For example, a conventional ECG monitor may employ five separate ECG electrodes to monitor ECG activity and use five separate cables to communicate the electronic signals from the electrodes to a bedside monitoring device. The use of such cables and the resulting "cable clutter," however, present numerous problems and disadvantages for the patients, the health care providers, and the monitoring systems themselves.
Such problems and disadvantages include, for example: (a) the use of cables makes the patient uncomfortable by restricting the patient's movement, (b) as the patient moves, electrical artifact can be generated on the cables that can trigger false alarms, (c) the cables must be made of high quality, expensive material so that they can withstand defibrillation, (d) because the cables establish a galvanic connection between the patient and the monitoring device, the patient must be isolated from the electrical mains of the monitoring device via bulky and expensive isolation circuitry, (e) cables can become tangled, damaged by other devices, or damage instruments by pulling them to the floor, (f) connecting and disconnecting cables to/from a patient to permit the patient to move can be quite burdensome, (g) the cables tend to pull on the transducers and frequently are dislodged from them, thereby causing false alarms, and (h) the cables must be cleaned, or even sterilized, each time they are to be used.
In the past, attempts have been made to minimize patient discomfort by "dressing" the cables and to increase the mobility of patients by making the cables as long as possible. Efforts also have been made to bundle sets of several cables, e.g., sets of three to five wires from ECG transducers, into single "trunk cables" in order to minimize the cable clutter near patients. In addition, in certain extreme situations, it has been the practice to restrain the patient physically to reduce the occurrence of one or more of the problems noted above.
Another prior art solution to the above-identified problems is to employ a telemetry transmitter located near the patient to transmit information acquired by physiological transducer(s) to a receiver, e.g., a receiver located at a centrally-located nurses station, that processes, analyzes and/or possibly displays the acquired information. A typical telemetry transmitter is battery operated and may be approximately the size of a bar of soap. Generally, one or more cables are connected between the physiological transducer(s) attached to the patient and the telemetry transmitter.
While telemetry transmitters tend to be significantly smaller and less expensive than bedside monitoring devices, these transmitters still are relatively burdensome to the patient since the patient is forced to carry the transmitter. It is primarily the transmitter portion of a telemetry transmitter and the batteries required to operate it that make the device relatively bulky. Because a telemetry transmitter must generate and transmit an RF signal, it consumes a significant amount of power. The charge level of the batteries of a telemetry transmitter therefore need to be evaluated frequently.
In addition, the cables used in connection with a telemetry transmitter pose many of the same problems identified above regarding the cables used with bedside monitoring devices. Further, because of the relatively high cost and fragile nature of telemetry transmitters, it is impractical in many situations to provide each patient with a separate device.
What is needed, therefore, is an improved device and method for monitoring the physiological conditions of patients.